This invention is directed to a hard body medication-dispensing device which can be implanted into a human patient so that the medication can be dispensed from a reservoir in the body manually from the device into the patient.
The present most commonly treated chronic condition which requires periodic medication is diabetes. Over about 2 million persons in the United States take daily injections for diabetes. Whether the doctor or the patient himself applies the injection, it is painful, cumbersome, and requires preparing the proper dosage and proper sterilization. In diabetes, insulin is periodically (at least daily) subcutaneously injected to maintain the sugar balance level. Periodic tests of sugar level permit the regulation of the amount of insulin medication taken. In present practice, the daily dose is adjusted in accordance with the need for insulin. Insulin is consumed throughout the day, but the injection of insulin at a periodic rate of more than once a day is cumbersome and painful. The present method of insulin medication thus has several drawbacks: First, it is difficult to foretell in the morning what the daily usage will be; second, each medication requires injection with its pain, cumbersomeness, and infection risk; third, a large dosage of insulin is not as physiologically desirable as several small doses.
There are other chronic conditions and diseases which require medicinal drug injections. One is cystic fibrosis where, in the later stages of the disease, substantially antibiotic levels are maintained in the patient. Antidote drug-dispensing may also be successfully achieved with an implanted dispensing device. In view of this understanding, it is clear that the term "drug" is used in its broadest sense and includes all therapeutic and diagnostic agents, such as hormones, vitamins, antibiotics, anticoagulants, cancericidal and spermicidal agents, vasoactive agents, and all other substances used to control, treat, diagnose, or otherwise affect physical or mental conditions of either normal or abnormal character existing in or on an animal body. In any such circumstances, it is desirable to employ an implanted medication-dispensing device of such nature that it can be manually operated to dispense when medication is desired, or can be electrically triggered from an implanted physiological sensor.
A review of the known prior art reveals that previously available implantable medicine-dispensing devices relied upon cumbersome methods to effect release of the medication when the release signal was applied from the exterior. These methods include electromagnetic coupling of questionable operability and the like. Other implanted devices control release of the medication into the body from a timed source, with the medicine being released whether or not the patient needed it. Others, such as a Blackshear (U.S. Pat. No. 3,731,681) continuously discharge medication without any opportunity for post implantation delivery control. In the case of diabetes, the patient usually checks his blood sugar level several times daily by simple urine tests to determine the amount of insulin required. The required amount is usually injected once a day (in the morning) and thus the dosage cannot be regulated with great accuracy with respect to need throughout the day. It is more desirable to cause medication dispensing at a plurality of times during the day and in response to need, rather than time. Other previously available devices dispense solid medication or waxy substances which have to be melted by body temperature for release. There is need for a liquid-dispensing device which is capable of injecting tiny, well regulated-as-to-volume amounts (if necessary) of liquid medication.